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Sometimes, a chance mutation in bacterial DNA allows certain bacteria to become resistant to certain types of antibiotic. When an antibiotic is given, only the non-resistant strains of bacteria will be ki...

Firstly, although fetal haemoglobin is better at binding oxygen, it is also worse at giving up oxygen to the tissues which need it. Secondly, if adults had haemoglobin with the same affinity for oxygen as...

The first stage in viral replication occurs when a virus attaches to the surface of a host cell. The viral nucleic acid (VNA) then enters the cell. The VNA then takes over the cell, altering the metabolis...

One of the things that you need to remember about Biology A Level is that you have to memorise the key points of the mark scheme. Something that I consistently struggled with when I was doing past papers ...

The sino-atrial node (SAN) is located within the wall of the right atrium, and acts like a pacemaker (it instigates the rhythms of the heart). The SAN sends out regular waves of electrical activity along ...